The famous and prolific German gun designer Vorgrimmler went to Spain at the end of the war to avoid prosecution (although he probably would not have been since I do not believe there was any hint he was directly involved in any War Crimes), and went to work for CETME. I believe these rounds were made for some experiments for them, and not for any general issue fo StG. 44s. In short, I believe they were part of the ongoing CETME experiments that lead to the CETME rifle, which was copied as the German G3 and produced in that form in many countries in the world.

I hope I am right. That is off the top of my head. I should look it up, but participation in a full CAS match yesterday put my knee problems back and I don’t feel like walking the stairs to my library.

Vorgrimmler, one of the Mauser design team developing the StG45 ( roller locked version of the Sturmgewehr), was first co-opted to ManuRhin, by the French Occupation Forces, in 1946. After a spell with the French, he left, went to Spain, and took the Roller-locked specs with him. The Spanish CETME ( Centro de Estudios de Materiales Especiales) worked on the developments of an Assault rifle based on the StG 45 features, using the 7,9 cartridge ( as did FN with their initial FAL Rifle, also in 7,9mm). Obviously they had quantities of StG44s for comparison purposes (acquired who knows how, as Spain was “neutral” during WW II–probably thru “nebulous” private dealing Postwar in Italy or Yugoslavia or Czechoslovakia).

BY the middle 50s, it was obvious that the US designed 7,62x51 T65 case design was going to be “THE” Postwar cartridge, and CETME switched over to this case design for its CETME-58 Rifles. The 7,9 died, for lack of use…
In anycase, during development, CETME required New Lots of 7,9 ammo in addition to the now ageing Wartime German supplies, and so Fabrica Nacional Palencia was tasked to run a “trial” batch, using brass for the cases…it was also a “Try-it and see” process for the ammo factory as well, in the manufacture of this ammo.

They probably did only several lots, enough for any Gun trials by CETME.
There is no sign of any general use by the Spanish Armed Forces during the 1950s of this cartridge.

The early CETME years are still unkown in detail to the wider Collecting community.

Eventually, Vorgrimmler left CETME and returned to Germany in the late 1950s, in Retirement (so to speak), however, he did see the fruit of his work (the H&K G3) adopted by the newly re-surrected German Army (BundesWehr).

Any Spanish members got any further info regarding CETME and the 1950s era??"??

Falcon - they are in that category of cartridges where most advanced collectors with any interest in them has one or more variations, but you seldom see one at a show or for sale. I suppose scarce is the best word - I could not class them as rare. When I was putting together a small collection of 7.92 Kurz, just one of each basic headstamp since I collected 7.9 x 57, I had no real problem getting one, but it took some correspondence.